>>717042406
deus ex is my favorite one, played that as a teen and defined the entire genre for me. I also played stuff like arx fatalis, thief, system shock, and would count a lot of RPGs like vampire bloodlines and morrowind too.
deus ex is an immersive sim because I get thrown into a scenario and told my goals, but it's up to me how I reach those goals while interacting in a pseudo-realistic manner with the world. npcs will react to your actions, and differently depending on stuff like alert, trespassing, hostility, stealth etc.
the immersive part also comes from the first-person perspective, so that you can get tricked into thinking that it's (you) that sneaking through the world.